dr. edward k.l. chan principal investigator the study on ... file-2 log likelihood statistics for...

Dr. Edward K.L. ChanPrincipal Investigator

The Study on Child Abuse and Spouse BatteringThe University of Hong Kong

立法會CB(2)2345/06-07)號文件LC Paper No. CB(2) 2345/06-07)

The Study on Child Abuse and Spouse Battering- Part Two

Objective: To develop and validate assessment tools to facilitate early identification of cases at risk of child abuse and spouse battering and timely intervention

Operational definition of spouse battering and child abuse

• Spousal battering is defined by physical assault, sexual coercion or injury, as measured by the revised Conflict Tactics Scales (CTS2).

• Child physical maltreatment is defined by severe or very severe levels of physical assault, as measured by the Parent-Child Conflict Tactics Scale (CTSPC)

Definition of risk assessment• Risk assessment is the process of identifying

and studying hazards to reduce the probability of their occurrence. (Boer, 1997)

• The process of evaluating individuals to (1) characterize the risk that they will commit violence in the future, and (2) develop interventions to manage or reduce that risk. (Monahan, 1994 )

Risk factors

Static risk factors

ImpactViolence

Dynamic risk factors

Physical Sexual

NeglectPsychological

Health

Mental Health

Risk assessment framework

Risk factors

Static risk factors

ImpactViolence

Dynamic risk factors

Physical Sexual

NeglectPsychological

Health

Mental Health

Prediction of risk

Development of risk assessment tools

• Phase A: Development of item pool– In-depth interviews and focus group

discussions with service users. – SWD and the Advisory Group on the Study on

Child Abuse and Spouse Battering– Pre-tested

• Phase B: Generation of Risk Assessment Tool – Representative household survey (December

2003 to August 2004) - A total of 5,049 adult respondents were successfully interviewed. The overall response rate achieved was 71%.

• Phase C: Preliminary logistic regression analysis – over 30 risk factors were identified for: – the perpetrator of spouse battering– the victim of spouse battering – the perpetrator of child abuse

• All these factors are significantly correlated to spouse battering and child abuse.

• Phase D: Factors included in the final model– Factors selected in the reduced model, that is,

the model used to design the risk assessment tools

Chinese Risk Assessment Tool for Spouse Battering Perpetrator

(Form A)

Logistic regression analysis (for perpetrators of spouse battering)

.000.000165.3691.056-8.540Constant

2.4851.7372.078.000164.180.091.731Partner’s disturbance (x13)

4.3431.9092.880.000125.457.2101.058Childhood witnessed parental violence (x12)

3.5441.7242.472.000124.264.184.905Criminal History (x11)

2.3401.3001.744.000113.742.150.556Face (x10)

.830.384.564.00418.428.197-.572Anger Management (x9)

1.5971.0541.297.01416.033.106.260Shifting Responsibility (x8)

2.3341.1671.651.00518.027.177.501Negative Attribution (x7)

2.2661.2721.698.000112.886.147.529Jealousy (x6)

2.8811.1221.798.01515.954.240.587Dominance (x5)

2.9541.0901.794.02215.284.254.585In-law Conflict (x4)

2.6171.1251.716.01216.284.215.540Indebtedness (x3)

3.6871.0261.945.04114.159.326.665Unemployment (x2)

3.3461.0681.890.02914.779.291.637Wife pregnancy/ adoption/postnatal

(within 1 year) (x1)

UpperLower

95% C.I. for Exp (B)Exp (B)Sig.dfWaldS.E.BRisk factor

For perpetrators of spouse battering, the required model equation is:

• A = -8.540 + 0.637X1 + 0.665X2 + 0.540X3+ 0.585X4 + 0.587X5 + 0.529X6 + 0.501X7+ 0.260X8 – 0.572X9 + 0.556X10 + 0.905X11+ 1.058X12+ 0.731X13

• P (risk (A)) = exp (A) / (1 + exp (A))

-2 log likelihood statistics for the logistic regression model

.000159.202-971.170Partner’s disturbance

.000122.783-952.960Childhood witnessed parental violence

.000122.022-952.580Criminal History

.000113.799-948.468Face

.00418.446-945.792Anger Management

.01416.100-944.619Shifting Responsibility

.00517.993-945.566Negative Attribution

.000112.765-947.951Jealousy

.01515.975-944.556Dominance

.03514.447-943.792In-law Conflict

.01615.831-944.484Indebtedness

.02814.832-943.985Unemployment

.03814.322-943.730Wife pregnancy/adoption/postnatal (within 1 year)

Sig. of the Chang

e

dfChange in -2 Log

Likelihood

Model Log Likelih

ood

Risk Factor

*The H-L test shows that the model explains the data well.

.61386.309Hosmer-Lemeshow (H-L) test for all risk factors regression analysis (Perpetrators)

Sig.Degree of freedom

Chi-square

100%33.07%66.93%Total

8.08%5.53%2.55%Happened

91.92%27.54%64.38%Not Happened

happenedNot Happened

TotalPredictedActual

All risk factors logistic regression analysis (perpetrators)

Classification table

• Sensitivity, which is the percentage of occurrences correctly predicted and is equal to (5.53%)/(8.08%) or 68.4%;

• Specificity, which is the percentage non-occurrences correctly predicted and is equal to (64.38)/(91.92%) or 70.0% ;

• Positive predictive value, which is the percentage of predicted occurrences that are correct and is equal to (5.53%)/(33.07%) or 16.7% ;

• Negative predictive value which is the percentage of predicted non-occurrences that are correct and is equal to (64.38%)/(66.93%) or 96.2% ;

• Overall accuracy, which is the percentage of predicted occurrences and non-occurrences that are correct and is equal to (64.38%+5.53%) or 69.9%.

• The optimal cut-off probability should be in the region of 7%.

0.0%

20.0%

40.0%

60.0%

80.0%

100.0%

95 85 75 65 55 45 35 25 15 9 7 5

Sensitivity /Specificity

SensitivitySpecificity

A Receiver Operating Characteristic (ROC) curve = 0.77

Chinese Risk Assessment Tool for Spouse Battering Victim

(Form B)

Logistic regression analysis (for victims of spouse battering)

.002.000149.839.849-5.996Constant

2.0551.3271.651.000120.184.112.502Feeling unsafe (x8)

2.3561.5701.924.000139.976.103.654Partner’s disturbance (x7)

4.7082.0083.075.000126.721.2171.123Childhood witnessed parental violence (x6)

5.5101.4562.832.00219.403.3401.041Sex Abuse History (x5)



2.9461.4222.047.000114.868.186.716Negative Attribution (x2)

2.7791.5132.051.000121.451.155.718Jealousy (x1)UpperLower

95% C.I. for Exp (B)Exp (B)Sig.dfWaldS.E.BRisk factor

For victims of spouse battering, the required model equation is:

• V = -5.996 + 0.718X1 + 0.716X2 - 0.632X3+ 0.750X4 + 1.041X5 + 1.123X6 + 0.654X7+ 0.502X8

• P (risk (v)) = exp (V) / (1 + exp (V))


.000119.329-855.471Feeling unsafe

.000136.877-864.245Partner’s disturbance

.000123.396-857.505Childhood witnessed parental violence

.00418.416-850.014Sex Abuse History



.000114.767-853.190Negative Attribution

.000121.270-856.442Jealousy

Sig. of the Change

dfChange in -2 Log Likelihood

Model Log Likelihood

Risk Factor


.055 815.211 Hosmer-Lemeshow (H-L) test for all risk factors regression analysis (Victims)


Chi-square

100% 33.02% 66.97% Total

7.10% 5.00% 2.10% Happened

92.89% 28.02% 64.87% Not Happened



All risk factors logistic regression analysis (victims)


• Sensitivity, which is the percentage of occurrences correctly predicted and is equal to (5%)/(7.10%) or 70.4%;

• Specificity, which is the percentage non-occurrences correctly predicted and is equal to (64.87%)/(92.89%) or 69.8% ;

• Positive predictive value, which is the percentage of predicted occurrences that are correct and is equal to (5%)/(33.02%) or 15.1% ;

• Negative predictive value which is the percentage of predicted non-occurrences that are correct and is equal to (64.87%)/(66.97%) or 96.9% ;

• Overall accuracy, which is the percentage of predicted occurrences and non-occurrences that are correct and is equal to (64.87%+5%) or 69.9%.

• The optimal cut-off probability should be in the region of 5.5%.

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

95 85 75 65 55 45 35 25 15 9 7 5Sensitivity / Specificity

Sensitivity

Specificity

Chinese Risk Assessment Tool for Child Abuse Perpetrator

(Form C)

Logistic regression analysis (for perpetrators of child abuse)

.000.000127.0641.567-8.150Constant


5.0911.3682.639.00418.385.335.971Violence Approval (x6)


4.8371.9043.034.000121.775.2381.110Jealousy (x4)

2.8951.2761.922.00219.776.209.653Extended Family Influence (x3)

6.4412.1143.690.000121.098.2841.306Receiving CSSA (x2)

6.5661.0252.595.04414.052.474.953Unemployment (x1)

UpperLower

95% C.I. for Exp (B)Exp (B)

Sig.dfWaldS.E.BRisk factor

For perpetrators of spouse battering, the required model equation is:

• C = -8.150 + 0.953X1 + 1.306X2 + 0.653X3+ 1.110X4 – 0.858X5 + 0.971X6 + 1.458X7

• P (risk (c)) = exp (C) / (1 + exp (C))



.00318.848-389.533Violence Approval


.000121.821-396.019Jealousy

.001110.237-390.228Extended Family Influence

.000118.265-394.242Receiving CSSA

.02714.895-387.557Unemployment

Sig. of the Change

dfChange in -2 Log Likelihood

Model Log LikelihoodRisk Factor


.461 87.719 Hosmer-Lemeshow (H-L) test for all risk factors regression analysis (Perpetrators of child abuse)


Chi-square

100%30.00%70.00%Total

5.95%4.10%1.85%Happened

94.05%25.90%68.15%Not Happened



All risk factors logistic regression analysis (perpetrators)


• Sensitivity, which is the percentage of occurrences correctly predicted and is equal to (4.10%)/(5.95%) or 68.9%;

• Specificity, which is the percentage non-occurrences correctly predicted and is equal to (68.15%)/(94.05%) or 72.5% ;

• Positive predictive value, which is the percentage of predicted occurrences that are correct and is equal to (4.10%)/(30%) or 13.7% ;

• Negative predictive value which is the percentage of predicted non-occurrences that are correct and is equal to (68.15%)/(70%) or 97.4% ;

• Overall accuracy, which is the percentage of predicted occurrences and non-occurrences that are correct and is equal to (68.15%+4.1%) or 72.3%.

• The optimal cut-off probability should be in the region of 5.5%.

0.0%10.0%20.0%30.0%40.0%50.0%60.0%70.0%80.0%90.0%

100.0%

95 85 75 65 55 45 35 25 15 9 7 5Sensitivity /Specificity

Sensitivity

Specificity

Usage of the tools

- The tool is designed to function as a triage, not for screening which could be done by using tools like AAS or CTS2.

- It is designed to help assessor assessing its probability of the occurrence of violence when risk factors continue to function and so decide the most appropriate way to handle it.

Target users of the tools

• The risk assessment tools are primarily designed for social workers, counselors and psychologists who have direct contact with the perpetrators and/or victims of domestic violence.

Functions of the risk assessment tools

• To facilitate early identification of domestic violence;

• To assist assessor in collecting fundamental information required to formulate further clinical assessment

Limitations of the risk assessment tools• Factors included in the tool reflect the most statistically

significant ones as demonstrated by the norm of respondents. Some factors with less significance may be valid for some particular cases.

• Accuracy of data collected depends heavily on the recollection of the respondents.

• While the tool is designed for self-report, there is always a possibility that the perpetrator may minimize, rationalize or deny acts of aggression against a spouse when responding to the questions asked in the tool.

• The scores generated by the tool show the optimum balance between sensitivity and specificity being calculated with statistical means.

• The scores are based on the assessment of risk factors. In addition, the scores only measure the probability of occurrence instead of the severity and frequency of violence. Direct assessment on the types, severity and frequency of violence used should be conducted.

• The tools should be treated as preliminary risk indicators; the assessor’s practice wisdom will be needed for final judgment. Second opinion from supervisor and senior practitioners should be sought.

People qualified to conduct risk assessment• social workers, counselors and psychologists

who have direct contact with the perpetrators and/or victims of domestic violence.

• People who wish to use the tools should ensure that the agency they work for has access to the information and resources needed to conduct a risk assessment of potential clients.

• To qualify to use the tools as part of the assessment procedure, the assessor should receive training in the tools’ usage.

• The training should enhance the assessor’s knowledge regarding the strengths and limitations of the tools and the standard procedures that need to be followed in conducting a risk assessment.

• An assessor with no prior experience of handling domestic violence should also receive trainingin understanding the dynamics of domestic violence, gender based violence and ways to elicit maximal information for objective judgment.

Administration of the tools

– Risk assessment should be conducted whenever the assessor can get in touch with a client.

– It is not necessary to wait for the appearance of physical signs like bruises and physical injuries, or the evolving of suicidal ideation before one is eligible for assessment.

– Only after the risk assessment can the assessor judges the potential risk the client bears.

– risk assessment should be done on a regular basis to monitor any changes in risk and to allow the assessor to readjust intervention to meet the client’s needs.

Eligible targets:• Perpetrator of spouse battering –

– people who reported or being complained of using violence against partner, usually the primary aggressor in cases of mutual combat.

• Victim of spouse battering –– people who reported being abused by a partner, showing fear

towards partner or being stalked by partner, usually the primary victim in cases of mutual combat.

• Perpetrator of child abuse –– people who reported or being complained of using violence

against a child, or neglect the needs for healthy development of a child.

– In case of mutual combat, • the assessor should identify the primary

aggressor by looking at the types and frequency of violence used, the severity of harm inflicted on the other partner, fear induced, power and control issues.

• If the assessor still finds it difficult to differentiate, the client may be asked to complete two sets of the risk assessment tools, one for the perpetrator of spouse battering and one for the victim.

– Non-perpetrator or non-victim may be assessed if assessor finds it necessary.

• Clients may display behaviors related to risk factors, for instance, unemployment and in-law conflict.

Use of data in clinical risk assessment

(1) consider all risk factors supported in the study

In-law Conflict

Extended Family Influence

Indebtedness

Receiving CSSA

Income

Unemployment

Wife pregnancy/ adoption/postnatal

Disability

Chronic ill

Perpetrator(Form C)

Victim (Form B)

Perpetrator(Form A)

Child abuseSpouse battering

Stressful Conditions

Social Desirability

Depressive Symptoms

Violence Approval

Substance Abuse

Anger Management

Shifting Responsibility

Negative Attribution

Jealousy

Dominance

Relationship Distress

Feeling unsafe

Afraid of partner

Partner’s disturbance

Childhood witnessed parental violence

Child Neglect

Sex Abuse History

Criminal History

Suicidal Ideation

Social Support

Self-esteem

Face

(2) The risk assessment tools are designed to measure the probability of occurrence of spouse battering and child abuse by detecting the presence of various risk factors that have been found to significantly correlate with the occurrence of domestic violence.

(3) Although the assessment is valid for the time of the interview, it does not measure changes in factors over time. The client should be reassessed on a regular basis to monitor changes he or she may demonstrate.

(4) employ multiple sources of information; the more sources of information the better

(5) be victim-informed(6) Instrument improves clinical judgment – but

clinician wisdom also plays important role(7) Risk assessment should lead to risk management.

• The tool is designed to function as a triage. it is designed to help assessor evaluate the urgency of a case by assessing its probability of the occurrence of violence when risk factors continue to function and so decide the most appropriate way to handle

• The more factors that are detected, the higher the likelihood domestic violence will occur.

Reference• Boer, D. P., Hart, S. D., Kropp, P. R., & Webster, C. D. (1997). Manual for

the Sexual Violence Risk - 20. British Columbia: The British Columbia Institute Against Family Violence.

• Kantor, G. K., & Jasinski, J. L. (1998). Dynamics and risk factors in partner violence. In J. L. Jasinski & L. M. Williams (Eds.), Partner violence: A comprehensive review of 20 years of research . USA: Sage.

• Monahan, J., & Steadman, H. J. (1996). Violent storms and violent people: How meteorology can inform risk communication in mental health law. American Psychologist, 51(9), 931-938.

• Mrazek, P. J., & Haggerty, R. J. (1994). Reducing risks for mental disorders: Frontiers for preventive intervention. Washington, DC: National Academy Press.

• Vincent C. (2001)Clinical Risk Management – Enhancing patient safety, BMJ, (2nd Edition)

• Kipp D. J. and Loflin E. M. (1996), Emergency Incident Risk Management, VNR.

The End

~ Thank You ~

dr. edward k.l. chan principal investigator the study on ... file-2 log likelihood statistics for...

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